


Egress from the Underground

by SpoopySis



Series: AT AUs [1]
Category: Adventure Time, Undertale (Video Game)
Genre: Abused Frisk (Undertale), Accidental Baby Acquisition, Canon Non-Binary Character, Finn's a blue soul, Gen, Past Child Abuse, Time Loop, finn lowkey has a baby sibling now, frisk is like three, idk thought it'd fit, its that, mostly implied - Freeform, u no those ut crossovers people used to write?
Language: English
Status: In-Progress
Published: 2018-11-07
Updated: 2018-11-28
Packaged: 2019-08-20 08:38:11
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,996
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16552508
Author URL: https://archiveofourown.org/users/SpoopySis/pseuds/SpoopySis
Summary: Exploring the Hall of Egress leads Finn to fall down into the Underground, where he meets another Human named Frisk





	1. Chapter 1

Summary: Taking a different path through The Hall of Egress sends Finn somewhere new.

The last thing he could remember was tripping into a seemingly endless dark pit. The cavern he'd entered after the trap sealed him in disappeared from view as he fell. Finn screamed into the darkness, fully expecting the bottom to lead to his death. Everything went black as he was surrounded by a strangely sweet smell...

Someone prodded at Finn's cheek, strangely insistent. He groaned and batted them away. "Five more minutes, Jake." Small hands grabbed his shoulder and shook. He reluctantly openopened his eyes to see that he was not at the Treehouse and the person waking him was not Jake.

"What The Stuff?" He scrambled away from the unfamiliar person.

The person watched him curiously, not saying a word. They picked up a stick and poked his leg.

"Quit it." Finn sat up and watched them closely. They looked different from most of the people he saw around Ooo. They seemed... more like him. More complete. "You're... a human."

The other human paused before nodding. They pointed at his hat with their stick, baring their teeth.

"I'm a human too, this is just a hat. See?" He pulled off the hat to demonstrate. That seemed to be the wrong thing to do, as they immediately raised their stick to defend themselves. "Woah calm down, dude! I'm a good guy... Do humans not wear animal hats down here? Are there other humans down here? I've only met a few humans before, what are they like? Oh, judging by your reaction they probably aren't very nice, huh?"

The human blinked, surprised by just how much he was talking. They relaxed and started to write something in the ground using the end of their stick. Finn moved towards them and read the word they'd scratched into the ground. "Frisk? Is that your name?" They nodded. "Nice to meet you, Frisk, I'm Finn. Do you know how to get out of here? Jake must be worried sick."

Frisk nodded and took his hand, leading him down a thin hallway. As the pair stepped through a doorway, Frisk stopped, as if waiting for someone. Finn jumped in surprise as a small yellow flower popped out of the ground, a bright grin on its face.

"Howdy! I'm Flowey. Flowey the Flower! Gee, its been a long time since any humans have come through here. You must be confused. Don't worry, Your old pal Flowey will show you how things work down here. Ready? Here we go!"

Before Finn had a chance to even react, a sharp tug on his chest caused an ethereal blue heart to fly out of his chest. A smaller red heart floated out of Frisk's chest, but they seemed unfazed. They almost looked tired.

"See that heart? It's your soul. The very culmination of your being." A feint box appeared around his and Frisk's souls. "Your soul starts out weak, but you can get stronger as you gain LV. What's LV?" Finn noticed his own LV was at 5 while Frisk's was much lower at just 1. "It's LOVE of course!"

Finn frowned, this wasn't right. His instincts told him something was wrong about what Flowey was saying. Finn realized he could still controll his soul and moved it in front of Frisk's as Flowey unleashed a barrage of white pellets. He yelped in pain as they made contact, proving his theory right. Flowey grinned, viciously. "You. Idiot. You thought you could protect your little friend? That's not how this world works. In this world, It's kill or be killed."

More pellets slammed into his soul, slowly whittling away his HP. Just as Frisk's HP was about to drop to zero Finn managed to pull out his sword and attack the murder happy plant. "What? But.. Its not your turn?"

A fireball appeared and knocked the flower away. Finn sighed with relief as a tall goat woman strolled up to them. "What a horrible creature, torturing a pair of poor innocent youths. Do not be afrafraid my children. I am Toriel, caretaker of the ruins. I pass through here every day to see if anyone has fallen down here. You're the first humans to come here in a very long time. Come. i will guide you. This way, children."

"Thanks a bunch, Mrs. Toriel. I thought we were goners there for a sec." Finn picked up Frisk, not wanting to let them trail behind too far. He was surprised at how calm they seemed after that whole situation.

Toriel smiled as she led them into a room that was far brighter than the last one. "It was no issue my child."

"You don't have to call me that, My name's Finn and this is Frisk." The younger human waved. "And I'm not a kid, I'm 16."

"It might have been a long time since I've seen a human, but I recall that most humans are not considered adults for a good few years more." She giggled.

Finn blushed in embarrassment. Frisk gave him a sympathetic pat on the cheek.

"Ah, you must be wary, there are many dangerous puzzles here in the ruins. Here, allow me to demonstrate." She walked along a group of large buttons, activating them in a specific order. Flipping a switch caused another door to open, to Finn's surprise. The next room also held a fairly simple puzzle that Frisk solved in moments.

"Living as a human in the underground, many monsters may try to attack you. when they do you will enter a FIGHT. I would like you to try to instead resolve the conflict peacefully. Try practicing on this training dummy."

"Why? If they're attacking us then we should fight back." Finn said

Toriel seemed surprised. "That may be how things are on the surface, but here all monsters coexist. There's no need to fight just because of a misunderstanding."

Finn thought about it. It didn't hurt to try a peaceful approach. He knew he could probably take any one who did try to actually kill him. "I guess I could try." He walked up to the dummy and saw his Soul pop out of his chest. It was significantly less shocking this time.

This time, once the box appeared, a series of options also appeared. Fight was Finn's first option, followed by Act. He selected Act, to Toriel's approval. _This is hardly the weirdest thing that's ever happened to me._ The Dummy immediately released his soul.

Toriel led them through several more puzzles that became more and more tedious, all of them fairly simple. Well, simple for Toriel. They barely managed to do anything before the Goat woman intervened and completed them for them. The final 'puzzle', was just walking down a- surprisingly long- hallway. Frisk actually seemed a bit amused when Toriel popped out from behind a large column.

"I have a few errands to run, please stay put until I return. Oh! Here is a cell phone, please call if you need anything." She handed Finn a phone, which he planned to hand to Frisk once Toriel left. "I'll be back soon."


	2. Chapter 2

Finn wasted no time in putting his number on Frisk's phone and putting Toriel's on his own. "There! Now if we get separated we can still contact each other." Frisk started to write something in the ground. "Oh right, you can't really talk. So yes or no questions only."

He sat down on the ground beside them. Leaning over he managed to read what they were writing. _Why did you come to the mountain?_

"Well, my brother told me about this weird cave that heard about from a friend so we decided to go check it out. I kinda went on ahead of him though and this trap sealed me in. I think we'll need to find another way out... What are you doing down here anyway way? and... how old are you, you look way too little to be on your own out in the wilderness."

They raised their hands to make a few gestures but paused, grabbing their stick again. _Running away. I'm 4._

Finn frowned. From what he knew, humans needed their parents much longer than just four years. Why would they run away? From who? There weren't any other humans around (Except Susan... and Simon, sometimes.) that would have raised them, so maybe they had lived with a mutant or animal family before.

But then... why had they been so scared when he said he was Human?

He decided against asking any of those questions. "Wow, and you can already read and write?" He beamed at them, "You must be like, a super genius or something!"

Frisk sunk into their turtleneck a bit at that. They seemed embarrassed by the praise. _It's not that special._

He shrugged off his bag and pulled out his sketchbook and a pencil. "Nah, don't put yourself down. I didn't learn anything like that till I was like nine. My Dad thought it was more important to learn how to fight. This might be easier than stopping to write in the dirt all the time." Frisk took them carefully, seemingly very surprised at his behavior. "I am a bit surprised that you don't have an animal hat yet. My parents found me with mine, I figured that humans just gave their kids hats at birth or some biz?"

Frisk giggled. _Have you been wearing that your whole life?_

"... I did not fall into a pit and almost die to get roasted by a toddler." Frisk stuck their tongue out and he laughed.

The cell phone Toriel left rang. As Finn answered he heard the sound of a dog growling as Toriel's muffled voice rang out in the background. "Bad Dog! Return that at once!"

"We should go help her, she sounds like she's in trouble." Finn stood, swinging on his backpack and grabbing Finn-sword off the ground. Frisk clutched the sketchbook to their chest with one arm and took his hand with theirs. He was a bit surprised but smiled and started to lead them to the next room... where the cell phone immediately began to ring.

"Hello children, you haven't proceeded have you? There are a few puzzles ahead that I have yet to explain. It would be dangerous to attempt them on your own..."

"Don't worry Ms. Toriel, Frisk and I are just fine."

"Oh! Wonderful. What a good brother you are Finn!"

Before Finn had a chance to process what she'd said, Toriel hung up. While they'd been talking Frisk had wandered into a pile of leaves and begun to crinkle through them excitedly. Finn opted to brush off Toriel's assumptions. "Come on, Frisk. Maybe we can catch up to Toriel."

The child bounded up to him excitedly. They took his hand as they began to proceed. It was very quiet as they walked, shadows skittering past the edges of his vision. Nothing approached them until they stumbled across a trembling insect. Finn attempted to ask them for directions but they burst into tears before he had the chance. Frisk seemed confused. _I expected more monsters by now._ They wrote.

"Maybe they're all... busy? Probably planning a surprise party or something." Finn couldn't help but feel unsettled as well. Normally investigating ruins and dungeons lead to many more encounters than he was facing here. "Or maybe they're just shy?"

Frisk frowned but said nothing.

* * *

 

He couldn't understand why Toriel had been so insistent on them staying put, The puzzles were surprisingly easy. Frisk even solved a few without him. But Frisk did seem pretty odd at times. When Toriel called again to ask them their preferred flavor, Frisk picked cinnamon before he had a chance to relay the question. They seemed to know about strange secrets before Finn could investigate.

It was a bit off-putting, but he figured they were probably a magic user of some sort.

When they finally found Toriel, she fretted over both of them for a bit before inviting them inside. 

Finn was floored by the sweet scent that filled his nose as he walked through the door. It was completely new but reminded him of the sweet cinnamony apple pies Tree Trunks would make.

"Surprise! It is a Butterscotch-Cinnamon Pie! I wanted you to enjoy living here... so I will hold back on Snail Pie for now." Finn paled at the thought. Toriel gave an understanding smile. "It is an acquired taste. Oh, I have more to show you."

The pair of humans followed the monster woman deeper into her home. "I've prepared a room for you both... I hope it is to your liking." Toriel pat Frisk on the head. "Oh! Is- something burning? Make yourselves comfortable." She hurried off before Finn could ask her any questions.

* * *

Frisk was still wary of the new human. They'd reset almost 50 times, nothing had changed in all that time. But here was this boy walking around, breaking the rules of this world. His determination was strong but nowhere close to theirs.

His LV was high but he didn't seem cruel, he actually seemed kind.

It was nice to have a companion through the ruins though.

They took note of the differences, throughout their journey. Namely, the lack of enemies. No one wanted to approach them when Finn openly carried his sword on his back. Or maybe his hat reminded them of Toriel? Either way, They had yet to see how he would react to a real FIGHT.

They crawled into bed, watching as Finn explored the room. It reminded Frisk of the first time they came through here.

"Hey, are you tired? You should get some rest, we can keep going later." Finn sat down on the floor and beamed at them.

They complied, knowing that was the best way to progress. When they woke, Finn seemed to be attempting to call someone and failing. He sighed and put his phone back into his bag. "Oh, you're up! Let's go ask Toriel about the way out."

Frisk took his hand, slipping their slice of pie into their inventory. They let Finn take the reigns talking to Toriel, they didn't want to waste too many pages of their new sketchbook. "Uhh, Mrs. Toriel. You've been really nice to us and I really appreciate it. But I really need to know the way out. I have to get back home, my brother is probably super worried about me."

Toriel looked up from her book. Her serene motherly smile lit up her face. "What are you talking about dear? This is your home now."

Finn's grip on their hand tightened. "I- You're right sorry to bother you." He forced a grin. "Hey Frisk, I saw some flyers for a bake sale, let's go check it out." He quickly pulled Frisk away from Toriel, leading them back to the entrance. Finn looked around rapidly, assessing the room. Noticing the stairs he began to lead them towards the ruins doors. Frisk struggled to keep up and Finn decided to simply pick them up to save time.

Over his shoulder, they saw Toriel begin to follow them down. "Children, what are you... No! That way is dangerous! They will kill you!" Toriel gave chase. No one was happy with this.

"Sorry Mrs. I have to get home." Finn skidded to a stop in front of the doors. "Aww, heck."

"You do not understand, every other human has died out there. I am only trying to protect you." Toriel grabbed Finn's free arm.

He jerked away. "I can take care of myself."

Toriel's face fell. "Prove it." With that, Finn was pulled into his first real FIGHT. 


	3. Chapter 3

Finn struggled to dodge Toriel's attacks, losing several points of HP in the first attack. Frisk checked his Stats.

Finn

Human (?)

LV: 5

HP: 97/105(150)

AT: 35(55) DF: 20(40)

Armor: Animal Hat Weapon: Soul Sword

*Something's different here...

They tried to understand why his HP looked like that. Was it because he was older? The monsters normally had high HP and Frisk had never Checked the stats of other humans before. But the second number... what was limiting it?

"Listen, I really don't want to fight. No one has to get hurt just let us go." Finn pleaded, seemingly still hesitant to fight back.

 _Why? You weren't planning to hesitate before? What's stopping you now?_ Finn glanced back at Frisk, standing between them and Toriel's attacks. _Well if that's what you're trying to do..._ They tugged on his shirt and pointed at the Mercy button. Finn seemed to understand and tried to Spare. Frisk guided his soul to a safe spot, happy that he was listening to their suggestions.

The humans continued to spare and dodge, Finn slowly getting the hang of the controls. Toriel began to hesitate. "What are you doing? Attack or run away."

Finn seemed to hesitate for a moment before sparing her again. "I need to go home, I'm sorry." Her attacks changed. Finn looked as though he was losing patience. His jaw was clenching in frustration and his movements were getting faster. They began to worry that he would attack. "Look! Just let us leave! I don't want to hurt you, this is getting exhausting."

"You must fight! There is no other way!"

He froze, a fireball sailing over his head. His right arm twitched, the pale skin changing color for a moment. "I do things My Way!" He spared again. Frisk could feel his determination spike for a moment before leveling out. "I can't fight you, it's against my code of honor."

Toriel's attacks stopped. "...What?"

"I can't fight a sweet old lady! That's like, super evil!"

Frisk facepalmed. That wasn't the worst reason for pacifism. Toriel looked unamused but her attacks stopped. "The monsters on the other side of that door will not hesitate as much as I have. Your existance is a blight to them. Continue if you will, but do not try to return. Frisk... Do you also wish to continue on?"

They froze. Did they actually have a choice here? So much was changing, maybe they could live here with Toriel instead of continuing... No. They couldn't leave their friends at the mercy of an unknown human. At least if they traveled with Finn they could ensure that no one was hurt.

Frisk nodded in afirmation, taking Finns hand. Toriel sighed. "Very well... please protect each other out there." She scooped them both into a warm hug. "Hehe... Pathetic is it not? I cannot protect you as it is you who wished to protect me. I really do worry far too much."

* * *

The hallway was very long and eerily silent. Frisk was gripping his hand with all their strength. Finn gave them a light squeeze back but said nothing. For some reason it was hard to think about what to say. Even as they stepped out into a large chamber with a single illuminated patch of grass, words failed him.

A high pitched voice caught his attention. "Clever. Very clever. You think you're pretty smart don't you, in this world it's kill or be killed." The flower's face shifted. "But you already know that, don't you?" It cackled in delight. "Did you think sparing one person would wipe away everything you've done? No. You'll fall back into your old habits again. Wait, where are you..?" Finn walked past the flower. "Hey!"

Finn pushed open the next set of doors, a fridged gust of wind sent the flower crawling back underground. He barely flinched when it popped back from the snow in front of him. "Why aren't you listening to me?!"

"You can't hurt me dude, you're just a flower. I've fought stuff that's way scarier than you. I know you're just trying to mess with my head!" Finn kicked some snow in the flowers face. "Just stay out of my way, I just want to go home."

Flowey growled and sank back into the ground. Frisk gave him a stange look. _you're not scared of him?_

"Nah, I've seen way scarier. C'mon. Let's find someplace warm." The pair of human's began to trudge through the snow, their footsteps echoing amon the towering trees. Strangely, Finn swore he could hear a third set of footsteps approaching from behind. But whenever he turned around he couldn't see anyone. Eventually they stopped in front of a bridge. "Uh-oh."

Finn peered over the edge, a bit of worry building at the lack of guardrails. _It doesn't look that deep, I don't think Frisk will get hurt if they fall..._

"H U M A N."

He shrieked, flailing a bit from shock. His hand went to his sword out of instinct as he spun around. It brought him face-to-face with a short skeleton wearing a faded blue hoodie and... fuzzy slippers? Not as intimidating as he expected from a monster. It held out a hand in greeting. Finn reached out cautiously.

 _pppppfffffffffftttttbbbb._ "heh. the old whoopie cushion in the hand trick... weird, you turned around before i told you to.didn't scare ya, did i?"

"No!" His voice broke a bit and he flushed with embarassment.

The skeleton chuckled. "anyway, the name's sans... sans the skeleton. you two are humans, right?" Frisk nodded, earning another laugh from Sans. "that's hilarious. i'm actually supposed to be on the lookout for humans right now... but i don't really care about catching anybody. my brother papyrus however, he's a human hunting fanatic. oh. that's him over there. quick, go through this gate. yeah go right across. my brother made the bars to wide to stop anyone."

Once they were across, Sans instructed Frisk to hide behind a lamp that was... near identical to the human. Finn found himself diving behind a pile of snow before the second skeleton appeared. "sup, bro."

"YOU KNOW WHAT'S 'UP' BROTHER. IT'S BEEN EIGHT DAYS AND YOU STILL HAVEN'T. RECALIBRATED. YOUR. PUZZLES! YOU JUST HANG AROUND OUTSIDE YOUR STATION! WHAT ARE YOU EVEN DOING!?"

"looking at this lamp. it's pretty cool, do you wanna look?"

Finn almost jumped out to protect Frisk but was halted by the second skeleton's loud cries of frustration. "I DON'T HAVE TIME FOR THAT! WHAT IF A HUMAN COMES THROUGH HERE? I WANT TO BE READY. I WILL BE THE ONE, I MUST BE THE ONE! I WILL CAPTURE A HUMAN. THEN I, THE GREAT PAPYRUS, WILL GET ALL THE THINGS I UTTERLY DESERVE. RESPECT. RECOGNITION. I WILL FINALLY BE ABLE TO JOIN THE ROYAL GUARD. PEOPLE WILL ASK, TO BE, MY 'FRIEND'. I WILL BATHE IN A SHOWER OF KISSES EVERY MORNING."

"hmm... maybe this lamp will help."

"SANS YOU AREN'T HELPING YOU LAZYBONES. ALL YOU DO IS SIT AND BOONDOGGLE. YOU GET LAZIER AND LAZIER EVERYDAY."

"hey, i've gotten a **ton** of work done today... a skele- **ton.** "

"SANS!"

"aw come on, you're smiling."

"I AM AND I HATE IT." Papyrus sighed dramatically. "WHY MUST SOMEONE AS GREAT AS ME, HAVE TO WORK SO HARD JUST TO GET SOME RECOGNITION."

"wow, it really sounds like you're working yourself... down to the **bone.** " Finn bit back a groan at that pun.

"I WILL ATTEND TO MY PUZZLES, AS FOR YOUR WORK... PUT A LITTLE MORE... **BACKBONE** INTO IT! NYEH HEH HEH HEH!... HEH."

"he's gone. you can come out now."

Finn rose out of the snow and brushed what was stuck to his clothes. He gave Sans a nasty glare. "Were you trying to get them caught? Jeez!"

"come on, it all worked out. besides, he's pretty harmless. actually... could you two do me a favor?" Finn almost said no... but he couldn't. "my brother's been kinda down lately, and seeing the two of you might just make his day. thanks a million. i'll be up ahead." The skeleton spun around and walked back across the bridge.

Finn sighed to himself. _This is going to take a while..._


End file.
